1. Field
The following inventions disclosure is generally concerned with automotive on-board diagnostics systems, data and power distribution networks and specifically concerned with on-board diagnostics networks and their coupling with smart power management systems arranged to provide power to connected video event recorders.
2. Prior Art
As automobiles generally include autonomous electrical power supply systems, it is important to carefully arrange and couple electrical power consuming devices to avoid overburdening the capacity of the supply. One understands completely how headlamps left energized while an engine is not running tends to render the power supply system completely drained in only a few hours. The headlamps consume the entire stored electrical capacity which is not renewed when the engine is not turning an electrical generator. When an engine is running, headlamps may be left on indefinitely as the alternator supplies ample energy to the headlamps while at the same time providing energy to recharge the storage battery. Accordingly, installation of automotive systems and devices which consume electrical power should be designed with a view towards consuming power in accordance with its availability.
It is quite well known in the automotive arts that non-essential electrical subsystems may be coupled in series with an ignition system whereby power is cut-off during times when the ignition switch is in an ‘off’ position. Vehicle operators who leave a car taking keys alongwith, necessarily cause power to be disconnected from those instruments so coupled via the ignition switch.
It is however sometimes desirable to leave some systems connected to the power supply even when an ignition system is in an “off” position. Power remote door lock systems require continuous power supply in order to remain operative. Accordingly, those systems are not coupled to the electrical power supply via the ignition, but rather, via a circuit which remains energized at all times.
Certain new advanced electronic systems are now being made available for use in conjunction with an automobile in service. One important new system is known as a “video event recorder”. Video event recorders are being deployed in service and fleet vehicles in a manner whereby a video record relating to vehicle use is electronically stored for further review. A primary example of these systems includes installation of digital video recorders with police cruiser type patrol vehicles. A police cruiser is frequently in a position where a video record is quite useful to have. In addition, more-and-more fleet type vehicles are being equipped with video event recorder systems. A vehicle fleet is an important corporate asset which benefits from protection via use of these mobile video systems.
Present, state-of-the-art video recorders are connected to the electrical power supply via a ‘hardwire’ or direct, unswitched connection. In this way, power is continuously provided to the video systems as long as the source is able to supply it. This enables the video system to capture video images even when an ignition key has been removed from the vehicle. However, the amount of energy consumed can be non-negligible. Indeed, it is entirely possible to completely the drain an automobile battery with these constantly connected video systems in a short period (a few days is certainly enough; under some circumstances a far shorter time will deplete a battery).
A further problem arises which is a bit more subtle but nevertheless important. Automobile type batteries are designed to supply a very large current in a short burst and to be recharged or ‘topped off’ shortly thereafter. Thus, the physical configuration of the battery supports a preference for a “fully charged” state. It is possible to configure a battery for efficient operation at reduced charge levels, but automobile batteries are not designed this way. A typical yacht battery in contrast, sometimes known as a “deep cycle” battery is designed for use in this manner. While it is certainly possible to use a deep cycle type battery in vehicles with ‘always-on’ video event recorders, this solution is a bit impractical. It is not desirable to impose new requirements on a vehicle's electrical supply system because a certain install configuration, i.e. “always on”, is somewhat desirable.
Another approach in the art suggests that a video event recorder be coupled to the power supply by the ignition switch. When the switch is in the “off” position, the video event recorder no longer consumes electrical power and remains inoperative until the ignition is reactivated. This is a valuable approach, but unfortunately leaves the video event recorder without power at certain times when it would be desirable to have power. This solution is also accompanied by the difficulty of providing an installation which couples to the ignition switch which may vary greatly from one vehicle model to another. It is a great disadvantage to attempt such connections to automobile power systems.
It is possible to provide a video event recorder with coupling to a power supply via an independent switch which may be operated without regard to the ignition. However such manual type switch couplings suffer from a great number of inconveniences and difficulties which need not be enumerated here.
It is thus desirable to provide a system which permits efficient coupling to a vehicle's power system, that does not overload a supply by consuming power during times when the system cannot sufficiently provide supply, and further to cooperate with standard equipment available in all models of vehicles. These, among other motivations, lead to systems described in detail here following.